Relevant offers

Carter gave no reasons for turning down the complaint, lodged after Diack told Parliament's commerce select committee that he was not aware former chief executive Don Elder had offered to appear before the committee.

It emerged that the day before the committee hearing, Elder's lawyer had written to the committee and Diack advising them that he was willing to attend.

The state-owned coalmining company's solicitor wrote back the same day, saying Elder would not be required to appear.

Cosgrove said such a blatant statement misleading Parliament from Diack must at least be investigated by Parliament for contempt.

Carter refused that, saying he had determined "no question of privilege is involved".

Cosgrove said Carter had failed his biggest test of non-partisanship.

"This is a slap in the face for taxpayers," he said.

"Allowing anyone to turn up and completely mislead MPs without consequences has made the select committee process a laughing stock."